The present invention relates generally to the field of lathes and mechanical processing of long, semi-rigid shafts (billets). More particularly, the device of the invention may be used advantageously as an attachment to a lathe to produce round cross-section articles with complicated profiled surfaces out of wood and other materials, including plastic, metal and composites. The instant invention should preferably be used to process wood workpieces.
Lathes equipped with automatic copying attachments are generally known. Russian Patent No. 338367 describes for example a profile turning automatic lathe allowing to make articles of round cross-section having complicated profiled surfaces. A rotating billet (typically with a square or round cross-section) is placed in the lathe and is processed with the help of several separate cutters moving in the plane of the billet's rotation axis. Rough and finishing cutters are fixed in the turning saddle and drawn along the main saddle in two directions: parallel to the billet's axis and radial or perpendicular to it. In the latter case the distance between the edge of the finishing cutter and the billet's axis is regulated with the help of a copying unit consisting of a copier (template) to which a guide roller (connected in turn with the turning saddle) is pressed with a spring. To process certain fine detail parts characterized by small radii of curvature, additional shaper tools are used: their edges correspond to the configuration of each separate section of the part. These shaper tools perform only cross-section turning and billet's cutting according to the required size. Cross-section cutters are set in working motion by turning, while the main saddle of the lathe moves using corresponding oscillating levers.
The shortcomings of this processing device include low productivity, the necessity of using a guide roller on the template (which results in limitations when processing profiled articles with small curvature radii), difficulty with cutting when heavy radial loads are imposed on the billet, a need for complicated readjustment when producing a new configuration of articles having different shapes and hardness, and a relatively short durability period of single-toothed tools of varied nomenclature.
These types of lathes, as well as planer tools having no additional shaper tools are already utilized in industry, such as TDS-2 (Russia), T-1500 (Italy) and others.
There is known a method of processing cylindrical billets using multi-toothed machining tools, as described in Russian Federation Patent No. 2064406. These tools are assembled in a form-milling cutter with two or more flat chisels held rigidly together so that wide enough edges are positioned in a common plane along the form-milling cutter's radii. This multi-teeth machining tool is rotated around the axis perpendicularly to the axis of the billet's rotation and is drawn along the billet's axis. This lathe's disadvantage is the inability to process complicated curved surfaces. It is possible only to change the diameter of the billet's machined surface to some extent while moving the tool along the billet's axis. Also, the cutting action power requirement increases in proportion to the width of the contact edge.
According to the Russian Patent No. 1653954, there is disclosed a lathe for processing articles as bodies of rotation where form-milling cutters with wide edges of various curvature are used instead of shaper tools. While processing profiled surfaces, a form-milling cutter is placed strictly perpendicular to the tangent of the curved surface. The device requires a complex mechanism of turning the form-milling cutter due to the introduction of an additional copier while the main saddle is moved lengthwise along the major copier. Each section of a billet with a different shape requires having another form-milling cutter of convex or concave edge as well as corresponding adjustment of the copier. The machined workpieces' curvature cannot be less than that of the corresponding form-milling cutter. The disadvantage of this processing method is its low productivity due to the inability to increase the number of complicated profiled teeth within the form-milling cutter's limited diameter; the necessity to use a complex copying assembly with two guide rollers; and the need for a mechanism for constant readjusting of the slope angle of the form-milling cutter, while processing selected sections of a workpiece. Additionally, the necessity of changing form-milling cutters to process parts with profiles having small curvature radii as well as the complicated adjustment procedure of the lathe and having to use expensive form-milling cutters reduce further the attractiveness of the device. Finally, a wide form-milling cutter causes decreased productivity due to billet's heavy radial loads.
Another similar device intended for processing articles as bodies of rotation is described in the Russian Patent No. 1653954 incorporated herein by reference.
The need therefore exists for a device adapted for efficient high-productivity manufacture of long articles (made of wood, metal, plastic, composites, etc.) having complicated curved surfaces.